section {
  width: 800px;
  height: 300px;
  background-color: skyblue;
  display: flex;
  flex-direction: row;
  align-items: flex-start;
}
div:first-child {
  width: 50px;
  height: 50px;
  background-color: hotpink;
}
div:last-child {
  width: 50px;
  height: 50px;
  background-color: hotpink;
  align-self: flex-end;
}
div:nth-child(2) {
  width: 50px;
  height: 50px;
  background-color: yellowgreen;
  flex: 1;
  align-self: center;
}
